How important is body language at the poker table?

[Bigron]

Despite psychologists' claims to the contrary, humans can direct their energy in other directions. The player appears to have played in a few games, judging by the blank look and lack of movement. Likewise, a person who publicly expresses their emotions is typically inexperienced in the game. The behaviour of individuals away from the table is another telltale sign to look out for. Contrast that with how they behave throughout the game. Excited people find it difficult to control their vigor. With this in mind, how important is body language at the poker table?